1. Field of the Invention
The present invention relates to the copying of source data that resides in one or more direct access storage devices (DASDs). More particularly, the invention concerns a copy method that, while write operations to source data are suspended, performs an instant virtual copy of the source data and also captures contents of a source dataset inventory. Later, the captured contents are used to create and/or update an analogous inventory for backup datasets.
2. Description of the Related Art
A number of DASD subsystems are capable of performing xe2x80x9cinstant virtual copyxe2x80x9d operations, also referred to as xe2x80x9cfast replicate functions.xe2x80x9d Instant virtual copy operations work by modifying metadata such as relationship tables or pointers to treat a source data object as both the original and copy. In response to a host""s copy request, the storage subsystem immediately reports creation of the copy without having made any physical copy of the data. Only a xe2x80x9cvirtualxe2x80x9d copy has been created, and the absence of any physical copy is completely unknown to the host.
Later, when the storage system receives updates to the original or copy, the updates are stored separately and cross-referenced to the updated data object only. At this point, the original and copy data objects begin to diverge. The initial benefit is that the instant virtual copy occurs almost instantaneously, completing much faster than a normal physical copy operation. This frees the host and storage subsystem to perform other tasks. The host or storage subsystem may even proceed to create an actual, physical copy of the original data object during background processing, or at another time.
With such benefits, instant virtual copy has been an important development in modern DASD subsystems, and a number of different embodiments have surfaced. As one example, International Business Machines Corporation (IBM) has developed the xe2x80x9cFLASH COPYxe2x80x9d technique, as described in different publications including U.S. application Ser. No. 09/347,344, filed on Jul. 2, 1999 and entitled xe2x80x9cMethod, System, and Program for Maintaining Electronic Data as of a Point-In-Time.xe2x80x9d A different fast replicate technique is the xe2x80x9cSNAPSHOTxe2x80x9d technique disclosed in U.S. Pat. No. 5,410,667 entitled xe2x80x9cData Record Copy System for a Disk Drive Array Data Storage Subsystem,xe2x80x9d which issued on Apr. 25, 1995. The foregoing references are hereby incorporated herein by reference.
Instant virtual copy techniques have been developed, at least in part, to quickly create a duplicate copy of data without interrupting or slowing foreground processes. A natural extension of this function has been the creation of a physical xe2x80x9cbackupxe2x80x9d copy of the source data, to aid in disaster recovery. Under one such technique, an operation such as xe2x80x9cFLASH COPYxe2x80x9d or xe2x80x9cSNAPSHOTxe2x80x9d operation is used to perform an instant virtual copy operation; this creates a virtual target volume identical to the source volume in all respects. Then, the target volume is taken off-line, which may occur automatically as a result of the instant virtual copy operation or manually at the direction of a system administrator.
Although the foregoing technique is useful in some respects, there are still certain challenges. Normal instant virtual copy operations can involve tens of thousands of files. Under these circumstances, it can be difficult to locate a particular dataset on a backup volume since the backup datasets are not catalogued. The usual procedure is to identify the source dataset on a source volume and then utilize other directories to identify the backup volume counterpart to that source volume. Then, the backup dataset is located by reviewing an inventory such as a volume table of contents (VTOC) aboard the backup volume. In another embodiment, an independent background process reviews contents of the backup volumes and creates an appropriate backup dataset inventory. This process, however, is consumptive of time and processing resources. Furthermore, if the source volume fails before the lengthy backup dataset inventory is compiled, the effort expended toward compiling this inventory is completely wasted.
For the foregoing reasons, then, known backup processes based on the instant virtual copy technique are not completely adequate for some applications due to certain unsolved problems.
A process of copying a body of source data is shown, where a backup manager quickly creates an accurate backup dataset inventory. While write operations to the source data are temporarily suspended, the backup manager performs an instant virtual copy upon the source data to create a backup copy. Also during this time, the backup manager captures contents of a source dataset inventory cross-referencing datasets in the source data and locations where those datasets are stored. The capture operation is especially rapid, and may be performed by reading the source dataset inventory into memory, performing an instant virtual copy of data including the source dataset inventory, copying the inventory into nonvolatile storage, etc. After the copy operation completes and writing of the source data resumes, the backup manager incorporates the captured source dataset inventory into a backup dataset inventory cross-referencing the names of datasets in the backup copy and their locations in the backup copy. Later, when a request occurs to access a particular backup dataset, the backup manager accesses the backup dataset inventory to locate the specified dataset in the backup copy, and ultimately accesses the specified dataset from that storage location.
Optionally, this process may be further enhanced in a number of different ways. For instance, where the source data is stored on a number of different storage media, an additional step may be performed before starting the backup operations. Namely, each source storage medium is paired with a counterpart backup storage medium having predetermined characteristics that match characteristics of the source storage medium. This effectively reserves the backup storage media before creating the backup copy.
Another optional enhancement concerns the use of copy pools. The invention may receive operator input of a xe2x80x9ccopy poolxe2x80x9d providing a shorthand reference for a specific group of source volumes. This shorthand eases the burden on operators to painstakingly specify multiple volumes for each time a storage operation involving those volumes is performed. Furthermore, when the copy pool definition is amended, this automatically applies whenever the copy pool is used in any future storage operations.
The foregoing features may be implemented in a number of different forms. For example, the invention may be implemented to provide a backup copy method. In another embodiment, the invention may be implemented to provide an apparatus such as a storage system or backup manager component configured to perform backup copy operations as discussed herein. In still another embodiment, the invention may be implemented to provide a signal-bearing medium tangibly embodying a program of machine-readable instructions executable by a digital data processing apparatus to perform backup copy operations. Another embodiment concerns logic circuitry having multiple interconnected electrically conductive elements configured to perform backup copy operations.
The invention affords its users with a number of distinct advantages. For example, the invention eases and speeds the process of locating a particular backup dataset because the backup datasets are inventoried. The invention also provides a number of other advantages and benefits, which should be apparent from the following description of the invention.